In coronary artery disease, the coronary arteries may be narrowed or occluded by atherosclerotic plaques or other lesions. These lesions may totally obstruct the lumen of the artery or may dramatically narrow the lumen of the artery. In order to diagnose and treat obstructive coronary artery disease, it is commonly necessary to pass a guidewire or other interventional instruments through and beyond the occlusion or stenosis of the coronary artery.
Percutaneous coronary intervention (PCI), also known as coronary angioplasty, is a therapeutic procedure used to treat the narrowed or stenotic section of the coronary artery of the heart due to coronary lesions or obstructions. A guide catheter may be used in PCI to support easier passage for another catheter or interventional device, such as, a microcatheter, stents or balloons, to access the target site. For example, the guide catheter can be inserted through the aorta and into the ostium of the coronary artery. Once seated in the opening or ostium of the coronary artery a guidewire or other instrument can be passed through the lumen of the guide catheter and then inserted into the artery distal to the occlusion or stenosis. Another example for the use of a guide catheter is found in femoro-popliteal intervention where femoral artery intervention can be effectively performed using radial or pedal access with guide catheters. Ruza et al. JAAC 11:1062 (2018).
However, guide catheters may encounter certain difficulties. The anatomy in the area for placement, e.g., the coronary vasculature, may be tortuous and the lesions themselves may be comparatively non-compliant. Moreover, when crossing comparatively non-compliant lesions, a backward force sufficient to dislodge the guide catheter from the ostium of the artery being treated can be generated. In order to improve backup support, U.S. RE 45,830 discloses a coaxial guide catheter which is adapted to be passable within a guide catheter. The distal portion of the coaxial guide catheter can be extended distally from the distal end of the guide catheter. The coaxial guide catheter includes a flexible tip portion defining a tubular structure having a lumen through which interventional cardiology devices such as stents and balloons can be inserted.
The guide catheter extension devices disclosed or available require construction of different tube portions of different characteristics and joining these tube portions together. For example, as disclosed in U.S. RE 45,830, the catheter extension includes a catheter tube portion which may include a soft tip, an inner liner component, a reinforced portion of the catheter body that is braided or coiled over the inner liner (flat or round wire braid composition or flat or round metal coil) and a polymeric cover section (e.g., Pebax, Nylon or other polymer material) which is melted or recovered over the reinforced catheter section, and a substantially rigid portion which may be made of stainless steel or nitinol tube. RE 46,116, RE45,760.
Another example of guide catheter design shows a guide catheter having a collar transition is made of a different material from the tubular portion. Here, the tubular portion is formed from multi-filament braided wire in order to reinforce the polymeric section. See, e.g., U.S. Pat. Nos. 8,048,032, 8,996,095, 9,352,123, 9,687,634, 9,764,118 and 9,993,613. However, these multicomponent designs and fabrication requirements can limit the mechanical properties and make fabrication complicated.
Thus, there remains a need for improved design for catheter bodies and catheter segments such as guide catheter extensions, and more generally, alternative designs for catheter tubes, that allow not only ease of fabrication, but also control of various characteristics of the tube, e.g., axial torque transmission, steerability, variable bending flexibility along the working length, pushability, collapse or kink resistance, etc., at any point along the tube. Controlling torqueability and flexibility at key points along the length of a catheter are important in order to enable the physician to negotiate access through various complex and often tortuous, anatomical vasculature which is often found in the coronary, peripheral or neurovascular systems.